Authenticated Resource Management in Delay-Tolerant Networks using Proxy Signatures Dominik Sch¨ urmann, J¨ org Ott, Lars Wolf March 18, 2013
Motivation Buffer Management Our Approach Evaluation Conclusion Mobile Communication in Rural Areas of Africa Unreliable cell infrastructure (power outages) Relative high monthly costs: Nigerians living on $ 2 a day or less ⇒ Delay-Tolerant Networks (DTN) (RFC 5050) Mit Mobile Money gegen ”finanzielle Apartheid” . 2009. url : http://www.zeit.de/digital/mobil/2009-11/m-money-africa ; Nigeria . 2012. url : http://topics.nytimes.com/top/news/international/countriesandterritories/nigeria/index.html Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 1
Motivation Buffer Management Our Approach Evaluation Conclusion Hop-by-hop Communication in DTNs Alice Bob Victor Eve Charlie Trudy Unknown meeting times Limited buffer space Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 2
Motivation Buffer Management Our Approach Evaluation Conclusion Example Attacks on Storage Buffers Denial-of-Service Flooding with big messages, differing in content, and forge source IDs. Set lifetime of bundle very high. Multicast Amplification Address bundle to multicast EID, set Report-to-EID to multicast EID More DTN-Specific Attacks. . . “Amplification by Fragmentation”, “Amplification by Custody Transfers”,. . . Victor Eve Charlie Trudy Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 3
Motivation Buffer Management Our Approach Evaluation Conclusion Example Attacks on Storage Buffers Denial-of-Service Flooding with big messages, differing in content, and forge source IDs. Set lifetime of bundle very high. Multicast Amplification Address bundle to multicast EID, set Report-to-EID to multicast EID More DTN-Specific Attacks. . . “Amplification by Fragmentation”, “Amplification by Custody Transfers”,. . . Properties of DTNs make attacks worse! What to do against malicious nodes flooding the network? Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 3
Motivation Buffer Management Our Approach Evaluation Conclusion Preemptive Buffer Management 1 Basic Idea Sign messages to Alice Bob authenticate their source ID Victor Partition storage equally between IDs of incoming Eve messages Charlie Trudy Example: Eve ’s Buffer (Max: 6 Messages) Stores messages coming from Alice, Victor, and Bob M 1 Alice M 2 Alice M 1 M 1 Bob M 2 Victor Bob 1 John Solis et al. “Controlling resource hogs in mobile delay-tolerant networks”. In: Computer Communications 33.1 (May 14, 2010), pp. 2–10. Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 4
Motivation Buffer Management Our Approach Evaluation Conclusion Request-Response Scenario Alice Bob Victor Eve Charlie Trudy Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 5
Motivation Buffer Management Our Approach Evaluation Conclusion Request-Response Scenario Alice Bob Victor Eve Charlie Trudy Example: Eve ’s Buffer (Max: 6 Messages) M 1 Alice M 2 Alice M 1 M 1 M 2 1. Request: Victor Bob Bob drop M 1 Alice M 2 Alice M 1 M 2 Bob R 1 2. Response: M 1 Victor Bob Bob Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 5
Motivation Buffer Management Our Approach Evaluation Conclusion Improving Fairness? Alice Bob Victor Eve Charlie Trudy Eve ’s Buffer: Original Scheme drop M 1 Alice M 2 Alice M 1 M 2 Bob R 1 2. Response: M 1 Victor Bob Bob Changed Affiliation of Response Bob M 2 M 2 Alice R 1 A ( B ) M 1 M 1 2. Response: Victor Bob drop M 1 Alice Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 6
Motivation Buffer Management Our Approach Evaluation Conclusion Scenario with Often Requested Server Node Alice 1 Alice 2 Charlie Eve Bob (= Server ) Alice 3 Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 7
Motivation Buffer Management Our Approach Evaluation Conclusion Scenario with Often Requested Server Node Alice 1 Alice 2 Charlie Eve Bob (= Server ) Alice 3 Eve ’s Buffer: Original Scheme drop M 1 M 1 M 1 R 2 R 3 2. Response: A 1 A 2 A 3 B B R 1 B , M 1 B Changed Affiliation of Responses M 1 R 1 M 1 A 2 R 2 A 2 ( B ) M 1 R 3 M 1 2. Response: A 1 A 1 ( B ) A 3 A 3 ( B ) B Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 7
Motivation Buffer Management Our Approach Evaluation Conclusion Cryptographic Background Signing Every node i has a public/private key pair � pk i , sk i � and an ID i Every node on the path should be able to verify the signature → Encrypt-then-Sign Encryption when sending message to Bob : c = Enc pk B ( m ) Sign ciphertext by Alice : σ = Sign sk A ( c ) Message to be send: M = � c , σ � Verification Buffering incoming messages based on source ID Verify source ID by verifying signature: Verify pk A ( c , σ ) Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 8
Motivation Buffer Management Our Approach Evaluation Conclusion Proxy Signature: “Delegation-by-Certificate” 2 A warrant ω defines the input space of the proxy signing function certificate pcert = Sign skA (00 � ID B � pk B � ω ) ciphertext c 1 = Enc pkB ( m 1 � ω � pcert ) with m 1 as request content request = � c 1 , σ 1 = Sign skA (11 � c 1 ) � A (forwarded hop-by-hop) B decrypt and verify signatures proxy signing key psk B = � sk B , pk A , ( ID B � pk B � ω ) , pcert � ciphertext c 2 = Enc pkA ( m 2 ) with m 2 as response content PSign pskB ( c 2 ) = � ID B , ω, pk B , pcert , σ 2 = Sign skB (01 � pk A � c 2 ) � response = � c 2 , Σ = PSign pskB ( c 2 ) � B (forwarded hop-by-hop) A 2 Alexandra Boldyreva et al. “Secure Proxy Signature Schemes for Delegation of Signing Rights”. In: Journal of Cryptology 25 (1 2012), pp. 57–115. Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 9
Motivation Buffer Management Our Approach Evaluation Conclusion Verification of Proxy Signatures Verification by Nodes Forwarding the Response Verify traditional signature Verify proxy signature by PVerify pk A , pk B ( c 2 , Σ) PVerify pk A , pk B ( c 2 , Σ) = Verify pk A (00 � ID B � pk B � ω, pcert ) ∧ Verify pk B (01 � pk A � c 2 , σ 2 ) ∧ ( c 2 ∈ ω ) . Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 10
Motivation Buffer Management Our Approach Evaluation Conclusion Application of Proxy Signatures pcert Restrictions Validity Restriction Certificate is only valid for a specific time frame Limited Response Responses are restricted to specific IDs by warrant ω Message Pattern One-time request-response Publish-subscribe Two-way communication Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 11
Motivation Buffer Management Our Approach Evaluation Conclusion Simulation with “The ONE” Simulator Does our approach improve request/response success probability? Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 12
Motivation Buffer Management Our Approach Evaluation Conclusion Simulation with “The ONE” Simulator Does our approach improve request/response success probability? What happens in presence of malicious nodes? Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 12
Motivation Buffer Management Our Approach Evaluation Conclusion Simulation with “The ONE” Simulator Does our approach improve request/response success probability? What happens in presence of malicious nodes? Scenario with Server Nodes (With and Without Proxy Signatures) 95 % nodes with 5 MB storage 5 % are “server” nodes with 50 MB storage 3 message types: Request, response, unidirectional Parameter Choice Movement Model Shortest Path Connectivity Bluetooth-like Routing Model Spray-and-Wait Map Helsinki city’s central area Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 12
Motivation Buffer Management Our Approach Evaluation Conclusion Only Benign Nodes Struggle for buffer space between message types Request/response success probability as a metric 0.40 with proxy signatures without proxy signatures 0.35 request/response success probability 0.30 0.25 0.20 0.15 0.10 0.05 0.00 20 40 60 80 100 percentage of generated request bundles Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 13
Motivation Buffer Management Our Approach Evaluation Conclusion 95 % Benign and 5 % Malicious Nodes 0.40 with proxy signatures, benign nodes with proxy signatures, malicious nodes 0.35 without proxy signatures, benign nodes request/response success probability without proxy signatures, malicious nodes 0.30 0.25 0.20 0.15 0.10 0.05 0.00 20 40 60 80 100 percentage of generated request bundles Dominik Sch¨ urmann | Resource Management in DTNs using Proxy Signatures | 14
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